Integration tests for XS Node.js bundler parity

[kriskowal]

Refs: #400

Establish tests that demonstrate that SES and XS native compartments have parity in integration with the kitchen sink behaviors of Endo/Agoric bundles.

Design

It should be possible to use @endo/compartment-mapper/bundle.js with a new "xs" tag to create a script that entrains a JSON bundle and importBundle with all its dependencies such that xst can run to completion and compare the output against an oracle. In combination with #2250, this will remove Babel from the transitive dependencies of importBundle.